页岩气的生成过程及其碳-氢同位素演化

The shale gas study is now a hotspot in the oil and gas exploration and development. In China, a certain achievement on shale gas development has been carried out and effective studies on the shale gas formation mechanism, geological characteristics and resource potential assessment, pool model, enriching factors, resource / reserves calculation and so on are performed. However, systemic study on the essential theory of shale gas is very weak and that this lag is after shale gas exploration and becomes a bottleneck for shale gas development. The geological conditions of shale gases formation are complex, there is a great difference of the gas generation and accumulation processes between the areas, the geological ages as well as the geological backgrounds. It is known that the are both kerogen-derived gas and oil-cracked gas in shale gas, however, the calculation method for estimating the gas account from oil-cracked or kerogen-derived gas is not yet established. A solution is required for the shale gas formation and accumulation under the complex geological setting. This study on the shale gas generation kinetics and C-H isotope composition is useful to understand well the shale gas generation, accumulation processes and post-generated changes, which is valuable in both the theory and practice for shale gas industry development.

页岩气已经成为当前国际油气领域的研究热点之一。我国页岩气勘探开发已经取得一定成效，在页岩气形成机理、地质特征及资源潜力评价、成藏模式、富集因素、赋存形式、资源量计算方法等领域开展了卓有成效的研究。然而，系统、深入的页岩气基础理论研究还非常薄弱；理论研究进展严重滞后于勘探生产实践，成了制约中国页岩气发展的瓶颈。我国的页岩气地质条件比较复杂，不同地区、不同时代、不同地质背景下页岩气的生成-聚集过程可能差别非常大。尽管已经了解页岩气中既有干酪根热解成因气，也有烃类的二次裂解气，但页岩气中究竟有多少来自干酪根热解气、有多少来自于烃类的二次裂解，目前国际上仍缺乏有效的计算方法。面对复杂的地质背景，我国页岩气的生成-聚集过程研究已成为无法回避的科学问题；页岩气的动力学及碳-氢同位素研究，有利于更好理解复杂地质背景下页岩气的生成、聚集过程与后期变化，对页岩气工业的发展具有一定的理论意义和重要的实际价值。

研制了新型热解仪、用该热解仪对2个II型干酪根进行了热解实验，分析了热解气碳-氢同位素的研究。对页岩气演化阶段进行了划分，分析了国内外主要页岩气田同位素特征；基于实验分析，提出了海相页岩气判识图版，可能对我国页岩气成因研究发挥一定作用。对龙马溪组页岩气判识结果显示，龙马溪组页岩气是干酪根热解气和油裂解气的混合，裂解气比例介于25-85%之间，与具体井位有关。